Package org.apache.pekko.cluster.ddata

Interface DeltaReplicatedData

All Superinterfaces:
ReplicatedData
All Known Implementing Classes:
AbstractDeltaReplicatedData, GCounter, GSet, LWWMap, ORMap, ORMultiMap, ORSet, PNCounter, PNCounterMap
public interface DeltaReplicatedData extends ReplicatedData
ReplicatedData with additional support for delta-CRDT replication. delta-CRDT is a way to reduce the need for sending the full state for updates. For example adding element 'c' and 'd' to set {'a', 'b'} would result in sending the delta {'c', 'd'} and merge that with the state on the receiving side, resulting in set {'a', 'b', 'c', 'd'}.

Learn more about this in the paper Delta State Replicated Data Types.

  • Method Details

    • delta

      scala.Option<ReplicatedDelta> delta()
      The accumulated delta of mutator operations since previous resetDelta(). When the Replicator invokes the modify function of the Update message and the user code is invoking one or more mutator operations the data is collecting the delta of the operations and makes it available for the Replicator with the delta() accessor. The modify function shall still return the full state in the same way as ReplicatedData without support for deltas.

    • mergeDelta

      DeltaReplicatedData mergeDelta(DeltaReplicatedData thatDelta)
      When delta is merged into the full state this method is used. When the type D of the delta is of the same type as the full state T this method can be implemented by delegating to merge.

    • resetDelta

      DeltaReplicatedData resetDelta()
      Reset collection of deltas from mutator operations. When the Replicator invokes the modify function of the Update message the delta is always "reset" and when the user code is invoking one or more mutator operations the data is collecting the delta of the operations and makes it available for the Replicator with the delta() accessor. When the Replicator has grabbed the delta it will invoke this method to get a clean data instance without the delta.